1. Technical Field
This invention relates in general to masks for medical purposes and, more particularly, to a mask for reducing gaseous leakage.
2. Description of the Related Art
Gas delivery masks are used throughout the medical industry for a variety of applications in which a gas is delivered to a patient. One significant application is the administration of anesthesia to a patient. A typical mask for this purpose is shown in FIG. 1.
The mask 10 of FIG. 1 comprises a face plate 12 having an outer seal 14 which interfaces with the patient's face. The mask 10 includes a port 16 through which inhalation gases are conveyed to the patient and exhaled gases are released. A breathing circuit 18 is coupled to the port. The breathing circuit 18 includes a first tube 20 for carrying the inhalation gas and a second tube 22 for carrying the exhalation gas. The first and second tubes 20 and 22 can be connected in a "Y" configuration as shown in FIG. 1, or in a concentric configuration where one of the tubes 20 or 22 is disposed within the other of the tubes 20 or 22.
A problem with any mask of this type, is that the mask 10 may separate from the patient's face. A typical example where the seal is lost between the patient and the mask occurs when the patient is holding the mask to his and her face and then passes out. In this instance, the gases intended for the patient will escape to the area surrounding the patient where they are inadvertently consumed by medical personnel. In the anesthetic field, these gases are often referred to as waste anesthetic gases or WAGs.
Exposure to WAGs can be extremely detrimental to the health of medical care workers. Some of the gases which are considered harmful include nitrous oxide and halogenated gases such as halothane, enflurane, methoxyflurane, trichloroethylene, and chloroform. The affected personnel include nurses, anesthesiologists, surgeons, obstetricians, gynecologist, operating room technicians, dentists and dental personnel, veterinarians and veterinarian personnel.
In the case of nitrous oxide, a pressure activated valve coupled between the gas source and the first tube 20, external to the mask 10, is used to prevent nitrous oxide from being delivered to the first tube 20, except when pressure caused by the patient's inhalation causes the valve to open. This type of pressure activated valve, however, is expensive and, therefore, not used in many cases.
Accordingly, there is a need in the industry to reduce waste anesthesia (or other) gases from entering the environment.